Some data storage systems, such as disk drive systems, use a voice coil motor (VCM) to position the head actuator arm relative to the rotational media for reading and writing to the storage regions. A disk drive data storage system typically includes one or more disks or platters for storing information, and the spindle motor may be used to rotate the platters. Subsequently, a read/write head may read information from or write information to the storage regions on the platters.
In order to accurately position the read/write head with respect to a storage region on a disk, variations in the position error between head and the servo data tracks written on the platters are kept at a minimum during operation.
However, external forces or disturbances often exist in the disk drive system that can interfere with position control of the VCM. One such disturbance is the repeatable run-out (RRO). RRO is an error signal that is repeated with each rotation of the disk. Because the effects of RRO are generally non-correctable, RRO can severely impact the overall performance of a disk drive system.